1. Field of Invention
The present invention relates generally to pneumatic tires, and more specifically to pneumatic tires designed to remain affixed to and in operative association with the vehicle wheel even upon deflation of the tire. Some varieties of these tires include devices designed to support the vehicle when the tire loses inflation pressure. Such tires are commonly known as "run flat" tires.
2. Description of the Prior Art
One basic problem with pneumatic tires is that the performance of the tires depends on the retention of pressurized air within the tire. Upon a condition where the pressurized air in the tire escapes, such as when the tire is punctured by a nail or other road hazard, performance of the tire can diminish rapidly. In most cases, the vehicle can only be driven a very short distance before it becomes inoperable.
Because of this deficiency, tire designers have long sought to develop a tire able to provide good driving characteristics and performance even upon deflation of the tire.
One of the key problems in providing such continued performance upon deflation is that of retaining the tire to the wheel Since the tire is normally retained on the wheel by the pressurized air within the tire pushing the beads and sidewalls of the tire outwardly against a wheel flange, the escape of the pressurized air through puncture or other road hazard eliminates the inner pressure. Absent this pressure, the tire tends to become disconnected and disassociated from the wheel and control of the vehicle becomes more difficult.
Previous efforts to address this deficiency have required a special wheel/tire combination. For various reasons this solution has not proven to be acceptable. One of the chief reasons for the ineffectiveness of the solution is the high cost of the special wheels which were required. These tire/wheel combinations have typically cost several times the cost of the typical tire and wheel combination. Other tire/wheel combinations required special mounting procedures and/or equipment. As such, they have never been commercially acceptable.
There was perceived a need for a new tire which could stay connected to a conventional wheel, even in a deflated condition, without the requirement of a special wheel. In other words, a tire which could be mounted to any conventional wheel, but which would be retained upon the wheel upon tire deflation and would continue to provide acceptable driving performance for an acceptable distance.
Efforts by others to address this need include European Patent application 0 475 258 A1, U.S. Pat. No. 5,131,445, U.S. Pat. No. 3,954,131, U.S. Pat. No. 4,193,437, U.S. Pat. No. 4,261,405, and European Patent application 0 371 755 A2.
In addition, several other attempts have sought to develop a bead configuration having certain advantageous properties and configurations. For example, in U.S. Pat. No. 4,203,481 a run flat tire is disclosed which is to be used in association with a special rim. In U.S. Pat. No. 1,914,040, a tire bead is disclosed having a rectangular configuration. Further, in U.S. Pat. No. 1,665,070, a tire bead is disclosed having a triangular configuration.
In commonly-owned copending application Ser. No. 07/954,209, which is incorporated here by reference, an innovative runflat device utilizing the herein disclosed inventive bead core is disclosed.